The present disclosure relates to the operation of rotary bodies, such as rotary kilns. In particular, the present disclosure relates a system and method for identifying the neutral roller skew position, and for setting the skew for rollers used to support rotary bodies.
Cylindrical rotary bodies, such as rotary kilns, are used in carrying out a large number of economically important processes. Such bodies typically includes a cylindrical shell portion that is supported by annular tyres spaced along the length of the tube. Each tyre is carried on a pair of opposed rollers, which in turn may be mounted upon a concrete pier or pad. The shell portion is rotated about its longitudinal axis, and is supported for such rotation by contact of the rollers with the tyres surrounding the shell portion. The rollers are correspondingly supported upon the piers or pads with the use of bearing assemblies.
Over extended periods of operation, the rollers may fall out of alignment, thereby causing their rotational axes to move out of parallel with respect to each other and not parallel or otherwise in optimum position with respect to the rotational axis of the shell. This is typically referred to as roller skew. The cost of replacing the tyres and/or rollers is relatively high. Thus, an important consideration in the operation of such rotary equipment is the maintenance of proper alignment between the surface of a roller and the supporting tyre to prevent uneven wearing of the respective surfaces and overloading the bearing assemblies. If the two are kept in proper alignment, a long life can be expected from the tyre and the rollers and the bearing assemblies.
Alignment relationships are complicated by the fact that such rotary equipment is typically constructed with the shell portion on a slight slope relative to horizontal to facilitate the flow of material therethrough. Thus, the shell exerts an axial force due to gravity, thereby causing an axial thrust load to exist on the rollers and their associated bearing assemblies whenever they are required to counteract gravity to keep the shell running on the rollers. In order to maintain proper alignment between the shell portion and the rollers, it has previously been necessary to periodically check the alignment by visual inspection or by sophisticated alignment measurements, to determine roller axial position as best possible. However, such measurements typically do not provide sufficient accuracies, must be made relatively often, are difficult to evaluate, very subjective, and in many instances are not dependably carried out by the operator.